Peaking ballast comprising inductive means having nonmagnetic gaps in flux paths



June 2, 1964 A. R. DAVIS 3,135,938 PEAKING BALLAST COMPRISING INDUCTIVE MEANS HAVING NONMAGNETIC GAPS IN FLUX PATHS Original Filed March 9, 1956 i .l. 9 Q8 T a Q7 99 INVENTOR. fi'g/a 0/? W5 United States Patent PEAKKNG BALLAST (SQ MPREHNG ENDUCTWE lvilJANS HAVING NUNMAGNETEC GAPS EN FLUX PATHS Ariel R. Davis, 3657 is. State, Sait Lake tiity, Utah (iriginal application Mar. 9, 1955, Ser. No, 570,515, new Patent No. 2,956,249, dated (let. 11, well. Divided and application Sept. 2'7, 196i), filer. No. 523,727

ll Claim. (Cl. 336 165) This invention relates to ballasts for dimming fluorescent lamps.

This is a division of my copending application Serial No. 570,515, filed March 9, 1956, now Patent No. 2,956,- 249, granted October 11, 1960.

An object of the invention is to provide ballast means that will ignite a fluorescent lamp over a range of intensities of illuminations.

Another object of the invention is to provide an inductive means to vary the intensity of illumination of a fluorescent lamp over a wide range.

Another object of the invention is to provide a ballast for fluorescent type lamps that produces a sharp voltage pulse for igniting the lamp over a wide range of intensities of illumination.

A further object of the invention is to provide an inductive current limiting means that Will ignite a fluorescent lamp at very low intensities of illumination with low RMS. voltages.

Other and further objects of the invention will be apparent from the following description taken in connection with the drawings in which:

FIG. 1 is a side view of a ballast; and

FIGS. 2 and 3 are fragmentary top and bottom views respectively of the ballast illustrating the nonmagnetic gaps in the side legs.

In FIGS. 1, 2 and 3 an embodiment of the invention is shown in which the magnetic flux paths of the reactor winding have a discontinuity to produce a change in flux characteristic. The ballast has a laminated center portion or member 9% and E-shaped portions @1, 92 on opposite sides thereof to provide parallel magnetic paths for the fluxes of the main winding 93 and reactor winding 94. The E-shapedportion 91 has legs 95 and 96 and an intermediate leg 97. The end leg 95 and intermediate leg 97 are coupled by a side leg 98, and the end leg 96 and intermediate leg $7 are coupled by a side leg 99. The E-shaped portion 92 has end legs 1% and Mil and an intermediate leg 102. The end leg 1% and the intermediate leg 102 are connected by a side leg 103, and a side leg 104. The end legs 96, 101, side legs 99, 104 and intermediate legs 97, M2 form parallel flux paths for the reactor winding 9a. A flux path for the main winding and the reactor winding is provided through the center portion 90, end legs 95, 1%, side legs 93, 103, 99, 1&4 and end legs 96, 101.

The E-shaped portions and the center portion are clamped together by suitable clamping means (not shown) to hold the end legs 95, 100, 96, M91 in tight magnetic contact with the center portion 96. The intermediate legs 97, M2 are slightly spaced from the center portion 90 to form air gaps 105, M6. In the flux paths for the reactor winding 94, a discontinuity is provided such as the slits or air gaps 107, N8 in the side legs 99, 104, respectively. On each end of the gap 107 are laminations 109, 110, and at each end of gap 108 are laminations 111, 112. The initial flux passing through the side legs 99,

Zigllidfidd Patented June 2, 1964 ice the thread through the laminations M9, lid, tilt and 112. These laminations provide a low reluctance for the initial flux provided by the main Winding 93. On saturation of these laminations, the flux path is determined by the reluctance of the air gaps E87, 1%. Since these gaps are wider and have a higher reluctance than the gaps M35, 1%, the main portion of the subsequent increase in flux I of the main windin Xi asses through the legs 97, 1%.

Some of the flux passes through the gaps 1%7, lltlg and the center portion 9a to induce voltage in the reactor winding additive to the input voltage for providing the re quired illuminating voltage. Thus, initially there is a flux change through the reactor winding 94 creating a voltage therein. But on saturation of the laminations Mid, 11%, 3111, 112, this flux change ceases and the flux passes through the gaps 165, 1%. On passage of arc current through the winding 94, the flux created by are current mustrpass through the air gaps 107, 1698. For this reason the saturation characteristics of the flux path through the side legs 99, we will be different from the flux of the reactor cores of the embodiment shown in FEGS. 1 through 4 of my Patent No. 2,956,249. The air gaps 107, 193 are turned to reduce the rate of saturation of the reactor core. This characteristic is another desirable feature imparted to the ballast.

As in the other embodiments described in the parent Patent No. 2,956,249 the intensity of illumination may be varied over a range of 590 to 1.

It is thus seen from the foregoing description that by inserting a discontinuity in the magnetic path coupling the main winding and reactor winding so that the rate of change of flux is abruptly altered during the fin cycle of the transformer winding and preferably during the initial stages, a peaking voltage may be induced in the reactor Winding. This'voltage should have maximum value in the order of 400 volts so that the lamp will be ignited at the low intensity of illumination.

The above-described ballast is compact in size and inexpensive to manufacture.

Various modifications and changes may be made without departing from the scope of the invention as set forth in the appended claim.

I claim:

A ballast comprising a reactor winding, a main winding, a ferromagnetic core having a center member with said reactor winding and said main winding wound thereon, E-shaped core members on the sides of said center member with intermediate legs between said windings and end legs at each end of said windings and side legs interconnecting said end and intermediate legs to complete the magnetic path of the flux of said windings, nonmagnetic gaps between said intermediate legs and said center member, non-magnetic gaps in said side legs adjacent said reactor winding, low flux capacity steel laminations bridging said gaps in said side legs to provide flux paths having low capacity low initial reluctance to induce a high voltage peak in said reactor Winding, and said intermediate legs adjacent said main winding ca rrying the remaining portion of the flux of said main winding.

References Cited in the file of this patent UNITED STATES PATENTS 2,578,395 Brooks Dec. 11, 1951 FOREIGN PATENTS 1,059,274 France Mar. 23, 1954 

